Solar Panel Glossary

Performance testing at reduced sunlight levels (typically 200 W/m²) to evaluate how well a module produces power under cloudy or early-morning and late-afternoon conditions.

An updated version of NOCT that measures module temperature under more realistic mounting and airflow conditions, typically yielding values 2-3 °C lower than NOCT.

The cell temperature reached under realistic outdoor conditions of 800 W/m² irradiance, 20 °C ambient, and 1 m/s wind speed with the module at open circuit.

A CEC-defined rating at 1000 W/m² irradiance, 20 °C ambient temperature, and 1 m/s wind speed that reflects real-world performance more closely than STC.

The universal laboratory benchmark for rating solar panels: 1000 W/m² irradiance, 25 °C cell temperature, and AM1.5G spectrum.

The operating current at which a solar panel delivers its maximum power output, always lower than Isc.

The ratio of a panel's actual maximum power (Pmax) to the theoretical maximum (Voc × Isc), expressed as a percentage that indicates how close the cell's I-V curve is to an ideal rectangle.

The highest power output in watts that a solar panel can deliver under specified test conditions, calculated as Vmp × Imp.

The maximum voltage a solar panel produces when no current is flowing, measured with the output terminals disconnected from any load.

The maximum current a solar panel produces when the output terminals are directly connected together with zero external resistance.

The percentage change in maximum power output for each degree Celsius the cell temperature rises above 25 °C, typically between -0.30% and -0.45%/°C for crystalline silicon.

The percentage change in open circuit voltage for each degree Celsius the cell temperature rises above 25 °C, typically between -0.25% and -0.35%/°C for crystalline silicon.

The operating voltage at which a solar panel delivers its maximum power output, always lower than Voc.

The percentage of incident solar energy converted to electrical energy by an individual solar cell, always higher than the corresponding module efficiency.

The annual percentage decline in a solar panel's power output over time, typically 0.4-0.7% per year for modern crystalline silicon modules.

The percentage of incident solar energy converted to electrical energy by the entire module, accounting for cell spacing, frame losses, and interconnection resistance.

The range of acceptable deviation from a panel's rated wattage, expressed as a ± percentage or wattage (e.g., 0/+5W means the panel will meet or exceed its nameplate rating).

A solar module designed to generate electricity from both its front and rear surfaces by capturing reflected and diffused light from the ground or surrounding surfaces.

Standard solar cells laser-cut in half to reduce resistive losses and improve shade tolerance, typically increasing module power output by 2-3%.

A cell design that sandwiches a crystalline silicon wafer between thin layers of amorphous silicon, delivering high efficiency, excellent temperature coefficients, and inherent bifaciality.

Solar cells cut from a single continuous silicon crystal, offering higher efficiency (20-24%) and a uniform dark appearance compared to polycrystalline alternatives.

A cell architecture that adds a dielectric passivation layer to the rear surface, reducing electron recombination and boosting efficiency by 0.5-1% over standard Al-BSF cells.

Solar cells made from multiple silicon crystal fragments melted together, identifiable by their blue speckled appearance and offering slightly lower efficiency (15-18%) than monocrystalline.

Narrow cell strips overlapped like roof shingles and bonded with conductive adhesive, eliminating busbars and cell gaps to maximize the active area and power density.

A next-generation cell architecture using an ultra-thin tunnel oxide layer and doped polysilicon for rear contact passivation, achieving cell efficiencies above 25%.

A thin optical coating applied to the cell surface or cover glass that reduces light reflection and increases the amount of sunlight absorbed, typically boosting output by 2-4%.

The outermost rear layer of a solar module that provides electrical insulation, moisture barrier protection, and mechanical durability, typically made of fluoropolymer or polyester films.

A diode installed across a group of series-connected cells that provides an alternate current path when cells are shaded or damaged, preventing hot spots and limiting power loss.

Ethylene-vinyl acetate sheets laminated above and below the solar cells that provide mechanical cushioning, moisture protection, and optical coupling between the glass and cells.

The weatherproof enclosure mounted on the back of a solar panel that houses the bypass diodes and provides the connection point for output cables.